UP to now, as a capacitive physical quantity sensor that outputs a capacitance changing corresponding to a physical quantity as a sensor signal, an acceleration sensor that outputs a sensor signal corresponding to acceleration has been proposed (for example, refer to Patent Literature 1).
Specifically, the acceleration sensor includes a silicon on insulator (SOI) substrate on which a support layer, an insulating film, and a semiconductor layer are laminated on each other in order. The semiconductor layer includes a movable electrode that is displaced corresponding to the acceleration, and a fixed electrode that is disposed to facing the movable electrode to produce a predetermined capacitance in cooperation with the movable electrode.
In the above-described acceleration sensor, when the acceleration is applied to the sensor, the movable electrode is displaced corresponding to the acceleration, and an interval between the movable electrode and the fixed electrode changes. For that reason, the acceleration is detected on the basis of the capacitance between the movable electrode and the fixed electrode.
However, in recent years, there is a demand to further improve a detection sensitivity. In the above description, an acceleration sensor is described as an example of the capacitive physical quantity sensor. Similarly, there is the same demand, for example, in an angular velocity sensor having a movable electrode displaced corresponding to an angular velocity.